1. An educational researcher sought to estimate the average number of close friends that students on a particular campus made during their first year of school. Questioning a random sample of 20 students completing their freshman year, he finds a sample mean of 3 close friends and a sample standard deviation of 1. Construct a 95% confidence interval to estimate the mean number of close friends made by all college students during their first year on campus. Round to two decimal places.

2. A local police department estimated the average speed of cars along St. John's Boulevard. With hidden radar, the speed of a random selection of 44 cars was measured. It yielded a sample mean of 53 km per/hr and a sample standard deviation of 5.9 km per/hr.

a. Construct a 98% confidence interval for the average speed of all cars driving on St. John's Boulevard. Round to two decimal places.

b. Express the confidence interval above in a complete sentence using standard phrasing

1. For the past five years a public relations firm has collected information about employee email and has found that employees receive on average = 41.7 emails per day, with = 18.5. Most of these emails are from other employees in the company, so in order to attempt to reduce the amount of emails sent between colleagues (as they can interrupt the flow of work), the company established a new priority list that all employees were to use before sending an email. One month after the priority list policy was established a random sample of 25 employees showed that they were receiving an average of x= 36.2 emails per day. Has the new priority list policy had any effect on the amount of emails being sent? Set alpha to .05 to test whether there has been a change (either way) in the average number of emails received per day per employee. Round to two decimal places, and show all five steps in your hypothesis testing.

Step 1

Step 2

Step 3

Step 4

Step 5